Lung cancer remains the leading cause of cancer death in the world for both men and women, and non-small cell lung cancer (NSCLC) accounts for the majority of lung cancer. Nearly 80% of lung cancer is diagnosed at an advanced inoperable stage, and current systemic therapy offers only modest benefits for lung cancer patients. The overall goal of this study is to determine the role of ?-catenin independent (i.e. non-canonical) Wnt signaling on the initiation and promotion of NSCLC. Our findings to date suggest two seemingly unrelated Wnt 7a functions: 1) that Wnt 7a acts as a tumor suppressor in normal lung epithelia, and 2) that activation of Wnt 7a activates ?-catenin independent (non-canonical) Wnt signaling through Fzd9, inducing activation of the tumor suppressor gene PPAR?. In previous work, we have demonstrated that Wnt 7a and/or Fzd 9 expression is frequently reduced in NSCLC, and that the loss of Wnt 7a and/or Fzd 9 is strongly associated with epithelial to mesenchymal transition (EMT), loss of cellular polarity, and increased susceptibility to lung carcinogenesis in mice. Based on these findings, we hypothesize that Wnt 7a/Fzd9 signaling plays a novel role in establishing and/or maintaining cell polarity, and functions as a tumor suppressor in the lung epithelium by regulating non- canonical Wnt (?-catenin independent) signaling. Moreover, our recent finding of frequent promoter methylation of Wnt 7a in human lung cancer makes Wnt 7a a potentially attractive future therapeutic target in the treatment of NSCLC. PUBLIC HEALTH RELEVANCE: Lung cancer is the leading cause of cancer death for both men and women in the United States. In fact, more deaths will occur this year due to lung cancer than breast, prostate, and colorectal cancers combined. The experimental strategies outlined in this project are designed to evaluate the contribution of the non-canonical Wnt pathway to lung cancer and to identify genetic targets of this pathway that could be used to develop potential small molecular therapeutic targets for the treatment of lung cancer.